AB1318 ULTRASOUND EVALUATION OF ACHILLES ENTHESIS AND GASTROCNEMIUS ARCHITECTURE IN PATIENTS WITH FAMILIAL MEDITERRANEAN FEVER: PRELIMINARY RESULTS FROM A CROSS-SECTIONAL STUDY
Authors: N. Güven, S. C. Güven, A. Kahveci, P. Bora Karsli, Ş. Ataman
Journal: Annals of the Rheumatic Diseases (2022)

Background Exertional leg pain and Achilles enthesitis are two musculoskleletal manifestations which have been described in familial Mediterranean fever (FMF) patients. Muscle performance is related both with mass and architecture. Measurements of muscle thickness and pennation angle in muscles with pennate structure, such as gastrocnemius, are representative of muscle mass and architecture, both of which can easily be measured via musculoskeletal ultrasound. Objectives Aim of this study is to evaluate thickness and pennation angle of medial gastrocnemius via ultrasound to evaluate muscle structure in FMF patients in order to detect implications of altered muscle condition and search for any relations with exertional leg pain/Achilles enthesitis. To our best knowledge this is the first study on the subject. Methods Consecutive FMF patients meeting Tel-Hashomer criteria between the ages of 18-65 were enrolled. A control group was formed from healthy volunteers with similar demographics. All ultrasound evaluations were performed by the same observer. Thickness and pennation angle of medial gastrocnemius was measured. Achilles tendon findings were scored according to OMERACT suggestions and total inflammation and structural damage scores recorded. Results A total of 40 FMF patients and 17 controls were enrolled. Clinical characteristics and ultrasound findings of subjects were presented in Table 1. All FMF patients were under colchicine treatment and 10% was also under anti-interleukin 1 treatment. Demographics were similar between groups. Right gastrocnemius pennation angle was significantly reduced in FMF group (degree, median(IQR): 20.8 (3.6) vs 22.7 (4.5), p=0.048). OMERACT ultrasound inflammation total scores were incresed on both sides in FMF group. When gastrocnemius and enthesis ultrasound findings were compared between FMF patients with and without exertional myalgia, no significant differences were observed. When FMF patients with and without enthesis findings in ultrasound examination were compared, again no significant differences in pennation angles and muscle thicknesses were observed. Table 1. Clinical characteristics and ultrasound findings in subjects FMF group Control group p N =40 N=17 Age, years, median (IQR ) 42.8 (23.0) 38.0 (15.0) 0.447 Gender, female, number (% ) 29 (72.5) 10 (58.8) 0.310 BMI, median (IQR ) 24.6 (5.3) 24.8 (5.7) 0.485 Presence of exertional myalgia, number (% ) 22 (55) Gastrocnemius thickness, mm, median (IQR ) Right 19.7 (2.9) 20.7 (5.6) 0.303 Left 19.6 (2.7) 20.7 (4.6) 0.321 Gastrocnemius pennation angle, degrees, median (IQR ) Right 20.8 (3.6) 22.7 (4.5) 0.048 Left 21.0 (3.3) 21.8 (4.7) 0.417 OMERACT ultrasound tissue damage total score, median (IQR) Right 2.0 (2.0) 2.0 (2.0) 0.659 Left 2.0 (2.0) 2.0 (2.0) 0.280 OMERACT ultrasound inflammation total score, median (IQR) Right 0 (2.0) 0 (0) 0.005 Left 0 (2.0) 0 (0) 0.023 Conclusion Our preliminary results imply altered right gastrocnemius structure in FMF patients regardless of Achilles tendon involvement and exertional myalgia, which may imply altered muscle function. By increasing the number of subjects we plan to achieve more accurate results. References [1]Eshed I, et al. Exertional leg pain as a manifestation of occult spondyloarthropathy in familial Mediterranean fever: an MRI evaluation. Scand J Rheumatol. 2012;41:482-486. [2]Kawakami Y, et al. Muscle-fiber pennation angles are greater in hypertrophied than in normal muscles. J Appl Physiol (1985). 1993;74:2740-2744. [3]Filippucci E, et al. Reliability of high-resolution ultrasonography in the assessment of Achilles tendon enthesopathy in seronegative spondyloarthropathies. Ann Rheum Dis. 2009;68:1850-1855. Acknowledgements I have no acknowledgements to declare. Disclosure of Interests None declared